BLOOD GLUCOSE CONTROL

Blood glucose control 2. Hormones 1. The goal is to maintain the level of glucose within a narrow range. If there is too little blood glucose, the body cells will not be able to get enough in and so will be low in energy If there is too much blood glucose, the body cells will not be able to get enough in and so will be low in energy 2. Hormones The hormones insulin and glucagon are the major controllers The hormones epinephrine and nor-epinephrine plus glucocorticoids are also involved in control at a minor level

INSULIN in feedback loops

Blood glucose Liver converts glucose to glycogen regulators Body cell uptakes more glucose coordinator result Beta cells in Islets of Langerhans release INSULIN Blood sugar drops Hypothalamus detects high blood glucose sensor high Blood glucose

Blood glucose low sensor Hypothalamus detects low blood sugar Blood sugar rises low sensor Hypothalamus detects low blood sugar Alpha cells in the Islets of Langerhans secrete GLUCAGON results Liver converts glycogen to glucose coordinator regulator

Insulin increases fat storage Glucagon increases fat release

Insulin action glucose insulin insulin receptor active ATP cAMP glucose uptake

Insulin action Stimulates glucose uptake into cells thus reducing blood glucose insulin insulin receptor active ATP cAMP glucose glucose uptake Now, skip ahead to “Insulin Actions”

2. Stimulates protein synthesis by increasing amino acid transport

3. Inhibits liver gluconeogenesis (ie the production of glucose from non-carbohydrate sources like protein and fats 4. Inhibits lipid breakdown Inhibits glycogen breakdown and stimulates glycogen synthesis

CONSEQUENCES OF A LACK OF INSULIN Hyperglycemia – glucose can’t get into cells and the osmotic effect of glucose leads to damage to eyes & kidneys

Muscle protein is broken down to release amino acids which are used to make glucose, leads to muscle wasting

Fats are broken down to convert lipids to glucose [lipolysis]

Diabetic ketoacidosis – breakdown in fat cells leads to production of free fatty acids and ketone bodies. Can lead to coma and death

5. Diabetes – the loss of blood glucose homeostasis a. person fails to make sufficient insulin Type I Diabetes b. Insulin must be added to the system test kit

Type II Diabetes a. The pancreas produces insulin but body cells do not react to it b. The body then produces more insulin c. Eventually the beta cells wear out and no more insulin is made d. To prevent this, a person must change their diet

Diabetic diet control 1. Avoid foods high in sugar 2. Eat complex carbohydrates 3. Eat food high in fibre 4. Keep diet low in fat

5. Eat more, smaller meals 6. Bedtime snacks high in protein 7. Exercise daily 8. Keep caffeine intake low 9. Keep alcohol intake low

6. Short term changes in blood sugar a. Blood glucose is regulated over time by insulin & glucagon but sometimes the body needs a sudden burst of glucose

b. These responses are called stress responses and they b. These responses are called stress responses and they elevate blood glucose only, there is no hormone to lower blood glucose in these responses c. Because this is not a feedback loop, stress can continue and problems will result [pg 389 Table 2] d. Stress responses [next slide]

Hypothalamus responds Long term Stress sensed by brain Short-term Hypothalamus responds Long term Pituitary gland releases ACTH to stimulate Spinal chord nerves stimulate Adrenal gland cortex Adrenal gland medulla Epinephrine & norepinephrine released Glucocorticoids released Amino acids  glucose Glycogen  glucose Fats  fatty acids Fatty acids  glucose Blood glucose increased Blood glucose increased

The glycemic index (GI) a numerical system of measuring how much of a rise in circulating blood sugar a carbohydrate triggers the higher the number, the greater the blood sugar response.

GI food type skim milk potato chips milk chocolate fresh pineapple white rice dates french fries baked potato roasted peanuts 14 49 31 98 75 85 54 103 61

Patterns of blood sugar over time for non -diabetics & diabetics

Blood glucose over time for different conditions. 1 2 3 4 5 TIME C B D A A- Normal response because blood glucose stays within a narrow range B. Type II Diabetic response because blood glucose does respond to hormones, but is slow to do so C. Type I Diabetic response / no insulin because blood glucose is falling very slowly D. Type I Diabetic response / Insulin at 2.5 because blood glucose does fall after 2.5

The Hunger Hormone: GHRELIN

Ghrelin Discovery Ghrelin was first described in 1999. They chose the name ghrelin because "ghre" is the Proto-Indo-European root of the word "grow," as ghrelin also stimulates the pituitary gland to release growth hormone.

Ghrelin Cells in the stomach secrete ghrelin.

The hormone ghrelin stimulates appetite Insulin and leptin suppress appetite

The rise in blood sugar following a meal causes an increase in insulin. The rise in insulin depresses ghrelin and so the desire to eat more is reduced. People with lower insulin levels suppress ghrelin less and so are hungrier more often.

Fluctuations in blood ghrelin levels.

Fat cells secrete leptin which decreases ghrelin levels. Basically having extra body fat signals the body to accumulate less extra fat.

Eating the same amount of calories of fat as of carbohydrate results in less suppression of ghrelin. This means that a diet high in fat leaves you hungrier!

Not all carbohydrates are equal at suppressing ghrelin. Drinks sweetened with fructose suppress ghrelin 50% as much as those sweetened with glucose. People who drink fructose drinks are more likely to choose fatty foods to accompany them and ghrelin may be involved in this.

When people diet, their ghrelin levels rise as the body tries to replace lost calories. I’ve found this great new dieting technique that really works

Surprisingly, people with naturally high blood levels of ghrelin tend to be slimmer than those with lower levels.

People who are obese tend to have less responsive ghrelin levels, so that eating does not reduce their desire to eat more. More ghrelin please

A lack of sleep has been shown to alter people’s eating habits. Just two nights of getting only 4 hours of sleep increased ghrelin levels by almost 30%.

Researchers are working on drugs to reduce ghrelin levels as possible ‘diet pills’.

Maybe people just have to realize that they are not all the same height so they have to accept that they will not all be the same weight!